In the field of human dentistry, the manufacture of fixed crowns, fixed bridges or partial dentures is usually preceded by manufacture of a rigid model corresponding to the affected mouth portion of the patient, i.e., the upper or lower jaw. The model is made from a mold or impression prepared by the dentist or his operative using an impression tray and various other components. For reasons of sanitation and economy, disposable impression trays are used which are available in various sizes for various mouth sizes, as well as upper and lower jaws. The dentist requires a selection of these on hand, as well as other necessary items as impression material base and catalyst, mixing pads and the like. Such items are preferably arranged for purposes of work efficiency and are maintained in inventory so as not to be out of a necessary item at a critical time.